Enhanced in vivo absorption and biodistribution of curcumin loaded into emulsions with high medium-chain triglyceride content.

The health benefits of curcumin have been demonstrated by several clinical studies, but its low bioavailability compromises its functionality. In this regard, emulsions have proven to be effective encapsulation systems for curcumin. Nevertheless, emulsions with a high oil content (50%) may offer some advantages due to the large amount of compound they can incorporate. Therefore, the aim of this work was to study the pharmacokinetics and biodistribution of curcumin when carried in optimized emulsions containing 50% MCT oil and a plant-based emulsifier (soybean lecithin) at 2 h or 4 h post-oral administration to rats. The most stable emulsion was obtained using 50% of oil and a surfactant-oil-ratio 0.1, through a microfluidization process. After the oral administration of the systems (150 mg curcumin/kg body weight), curcumin glucuronide was the main compound present in plasma (AUC0-t = 1556.3 ng·h·ml-1), especially at 2-4 h post-administration. The total curcuminoid bioavailability was increased by 10.6-fold when rats were fed with the curcumin emulsion rather than with a control suspension. Moreover, rats fed with the emulsion showed the highest accumulation of free curcuminoids, which present the highest biological activity, in the liver (129 ng curcumin/g tissue) and brown adipose tissue (193 ng curcumin/g tissue). The obtained results are of great interest since the presence of curcumin in the brown adipose tissue has been shown to play a relevant role in the prevention of obesity and its related metabolic disorders.

The lipid type affects the in vitro digestibility and ß-carotene bioaccessibility of liquid or solid lipid nanoparticles.

Solid lipid nanoparticles (SLNs) are emulsion-based carriers of lipophilic bioactive compounds. However, their digestibility may be affected by the solid lipid phase composition. Hence, the aim of this work was to study the in vitro lipolysis kinetics as well as the relationship between the lipid digestion, micelle fraction composition and ß-carotene bioaccessibility of SLNs with different solid lipids, being blends of medium chain triglyceride (MCT) oil, glyceryl stearate (GS) or hydrogenated palm oil (HPO) as compared to liquid lipid nanoparticles (LLNs) with pure MCT. SLNs formulated with GS were fully digested, similarly to LLNs. However, HPO-containing SLNs presented slower lipolysis kinetics during the intestinal phase at increasing HPO concentration. Despite this, HPO-SLNs showed higher ß-carotene bioaccessibility, which was related to the higher amount of monounstaturated free fatty acids in the micelle fraction. Thus, this work provides valuable insight for designing delivery systems of bioactive compounds with optimal functionality.

Curcumin-loaded nanoemulsions stability as affected by the nature and concentration of surfactant.

Nanoemulsions containing 0.5% w/w corn oil enriched with 0.4% w/w curcumin, sodium-alginate (1.0% w/w) and 0.5, 1.0 or 2.0% w/w of surfactant, were assessed, including particle size (nm), ζ-potential (mV) and turbidity over time. Furthermore, nanoemulsions encapsulation efficiency (EE), antioxidant capacity (AC) and release kinetics were studied. Nanoemulsions showed particle sizes ≤400±3 nm and effectively reduced droplets interfacial tension with negative ζ-potential values (≤-37 mV), regardless the concentration of surfactant. Nanoemulsions with 2.0% w/w lecithin did not suffer destabilization phenomena during almost 86 days of experiment, whereas those containing Tween 20 or SMP at the same concentrations were destabilized after 5 days or along 24 h, respectively. Despite EE of nanoemulsions was above 75%, just in lecithin-stabilized nanoemulsions it was directly correlated to AC. Therefore, this work contributes to elucidate the influence of lecithin, Tween 20 and SMP on curcumin encapsulation and stabilization of curcumin-loaded nanoemulsions.